How to close client and refresh agent gracefully?

[SHxKM]

After much help from @iansrobinson, we are using this library in our DEV and PROD environments.

One thing I'm deliberating how to handle is closing the GraphTraversalSource we've built, as well as the ClusterEndpointsRefreshAgent. They both expose a close() method, but I'm wondering if we have some elegant way to "wait" for pending queries, without holding state. The service should stop receiving requests from the load balancer on rolling a new version (or pod restart), so we can rely on that, but I'm wondering if something nice is also exposed.